1. Field of the Invention
The invention relates to finishing metallic and non-metallic surfaces by abrasion techniques.
2. Brief Description of Related Art
The literature is replete with descriptions of apparatus and methods for finishing the surfaces of a variety of articles of manufacture. Representative of such articles are tools and instruments, many having complex geometric shapes and curvilinear surfaces.
One of the problems in finishing complex surfaces, especially curvilinear surfaces, is the need to draw the article across an abrasive surface while continuously changing the angle so as to accommodate the geometric shape thereof. The finishing of complex surfaces usually requires skilled hands and experienced craftspeople. Even experts find it difficult to follow many complex surface shapes, due to the demanding control required.
In the manufacturing industry, establishing conditions for a finishing process to obtain a specified surface topography is also not problem free, since many interacting factors are involved. Under ideal circumstances, the factors to be considered involve the operational setting of the machine (e.g., the geometric characteristics of the abrasive tool, the work speed, the tool feed rate and the type of cutting fluid used). Even under ideal conditions it has been only possible to calculate the theoretical roughness developed in a machining operation for the simplest process, i.e., single-point tool cutting. The fact that it is not possible to fully specify the character and surface roughness scale and topography of a surface remains a serious problem for production/design engineers.
One aspect of the present invention concerns the finishing of surfaces on tools and instruments. For example, dental, veterinary and medical instruments may have sophisticated shapes which can only be obtained with an exacting and complex finishing procedure.
For example, the U.S. Pat. No. 4,509,268 (Marquam et al.) and U.S. Pat. No. 4,821,462 (Moore) describe apparatus for sharpening dulled surfaces of dental curets. Marquan et al. says "A common sharpening error encountered is failure to restore the cutting edge to the proper angle. Another common error is failure to maintain the proper blade shape with the cutting edges parallel and the toe smoothly rounded". Marquam et al. approaches the problem by providing an adjustable protractor-like guide for positioning the curet blade at a proper angle with a flat sharpening stone. The operation of the guide requires the operator to determine the proper angle (various curets having different blade angles) and to sight along the guide to determine that the proper angle has been selected. It is necessary to re-position the curet for a second blade edge angle. Moore in the later U.S. Pat. No. 4,821,462 describes a similar protractor device, improved by the association with a pair of flat, spaced apart sharpening stones and an index for identifying the proper angle of an inserted blade. The difficulty with both devices remains in that a degree of training and expertise is required to use them, including the knowledge of proper angles required. In the hands of the untrained, a curet can be damaged beyond repair.
The present invention is an apparatus that will accurately provide an exactly shaped cutting edge to a dental curet. The apparatus not only provides an exact shape for the curet cutting edge, but it does so with precision every time. A reason that this apparatus works so well is its simplicity. With this apparatus, the dentist or technician performing the finishing need not be as careful in drawing the instrument across the abrasive surface. Although the instrument itself is generally held at certain angles with respect to the abrasive surface, even this is not critical. The apparatus of the invention has one or more specifically shaped abrasive surfaces to guide and finish the instrument surface. These abrasive surfaces create an exact shape for the cutting edge of the curet. The shape provides the fineness and delicacy of its original design. Reported at the recent 1996 World Workshop in Clinical Periodontics, was the extensive review of the current literature by Quirynen and Bollen. Using an evidenced based approach, they concluded that both surface free energy and roughness play major roles in the initial adhesion and retention of oral microbes. Quirymen and Bollen reported the above findings to be of sufficient importance to demand clinical attention during therapy, to achieve the smoothest possible root surface. Therefore, the abrasive surface component of the apparatus of the invention creates not only an exact shape of the desired cutting edge of a curet, but a cutting edge with the proper edge fineness and delicacy required in dentistry based on current research.
The present invention is, however, not limited to the finishing of tools and instruments for use in the medical, dental and veterinary arts. The present invention reflects the discovery that many surfaces can be carefully finished, shaped or sharpened to obtain the objectives required. This may be carried out by placing them in contact with abrasive surfaces that mirror completely, or partially and selectively, the desired surfaces of the objects to be finished. The present invention will aid in achieving the objectives of a specified manufacturing process (for example, surface topography or surface geometry, cross-sectional geometry, and surface finishing) by providing apparatus having abrasive surfacing contours that have selectively planned abrading contact areas and relief surfaces (non-contacting areas) to permit a desired outcome of a finishing process. One of the main advantages of this invention over the prior art is that the apparatus of the invention has built-in, selectively placed relief surfaces. By controlled movements of the tool or instrument, or part thereof, through the apparatus, one can impart a specific finish such as shaping, grinding, polishing, cleaning, buffing or sharpening to selected surface zones, while leaving other zones unfinished.
The movement of the tool or instrument, or part thereof, can be independently, or dependently with the abrasive surfaces and relief surfaces in multiple or single-spatial planes such as linear, elliptical, or circular, depending upon the finishing objectives and surface configuration.
The relief surfaces also provide a means by which abrasive residues can be removed from interfering with the apparatus operation during the finishing process and to direct introduced dry and liquid cutting fluids, lubricants and gases, such as graphites for temperature and lubrication control.
The relief surfaces provide a means by which certain surface zones on articles to be finished can be left undisturbed while contiguous zones are abraded or shaped. This results in the desired shape (by selectively abrading and selectively non-abrading).
This invention differs from the prior sharpening arts due to its selective, reshaping capabilities, as well as its ability to resharpen a tools' worn surfaces. In other words, surfaces can be selectively and specifically shaped to restore the complex angles and shapes of the working edges of an instrument, or a component of a complex machine or apparatus/device.
Metal surfaces are finished (non-metal can also be finished with the apparatus of the invention) by abrasion. Metal articles include, without limitation, screws, arrow heads, hammer heads and drill bits. Almost any instrument, tool or surface that can be drawn or turned on an abrasive surface can be finished by the apparatus of this invention.
The abrasive surfaces of the apparatus of the invention may be multi-segmented such as mirrored halves, which invertly correspond to the complex, geometric surface of the article to be finished. The article is placed in a first half of the apparatus and the corresponding, second half is then placed over the article. Depending on the surfaces to be finished, the article is then turned in or pushed into the apparatus. The forcing of the article through the apparatus causes a finishing of the surfaces of the article. If one defines the desired shape and surface finish (degree of smoothness), one can selectively place abrasives, lining those internal inverted channels to finish the article or surface according to desired specifications.
To date, there is no non-automated finishing device that will produce the proper cutting edge for the complicated, intricate type of instruments employed by hygienists, dentists, doctors and veterinarians. The earlier sharpening devices or procedures are very crude and unrefined with respect to maintaining small, delicate surface shapes of a curet. Additionally, the cutting edge of a dental curet is often delicately shaped during manufacture. The attempt to shape and, therefore, accurately reproduce this cutting edge to its original, precise surface configuration is rendered futile when utilizing a flat, sharpening stone.
The invention contemplates a variety of finishing processes. For example, finishing includes grinding, honing, shaping, polishing, cleaning and buffing. In other words, this invention has an objective that differs from simple sharpening required of such devices as razor blades, knives and other sharp edges having flat surfaces meeting at an edge. Human medical, veterinary and dental care require and deserve dental and medical instruments that are of superior and sophisticated shapes, shapes which must be maintained with exacting and complex detail.